The relative value of hepatobiliary scintigraphy vs. real-time ultrasound for the identification of acute cholecystitis was evaluated. No significant difference in sensitivity (97% vs. 97%) existed between the two modalities. Scintigraphy demonstrated better specificity (93% vs. 64%) and predictive value (77% vs. 40%). Although real-time ultrasound provided improved sensitivity over static gray-scale imaging for identification of gallbladder disease, hepatobiliary scintigraphy remains the procedure of choice for acute cholecystitis detection.